U.S. Pat. No. 6,010,095 discloses a method of detecting ice in all kinds of aerospace applications. The contents of U.S. Pat. No. 6,010,095 are incorporated by reference in their entirety. An embodiment of this patent was performance tested in the world's largest icing wind tunnel at NASA Glenn in Cleveland Ohio. The tested embodiment conforms to the Society of Automotive Engineers' Aerospace Standard 5498 entitled “Minimum Operational Performance Specifications for Inflight Icing Detection Systems” core paragraph 5.2.1.1.1; and has been included in the SAE's Aerospace Information Report 4367, a compilation entitled “Aircraft Inflight Ice Detectors and Icing Rate Measuring Instruments”, paragraph 4.11.
In terrestrial applications the airflow can be weak or completely still. Surface tension presented by the inside angles and radiuses of the aerospace ice detecting optics can retain standing water after the detected ice has melted away, causing false ice alerts.